The present invention relates to a method of folding packing blanks along preformed bend lines.
The present invention is particularly suitable for use on cigarette packing and/or cartoning machines, hereinafter referred to generally as "packing machines", and to which the following description refers surely by way of example.
On cigarette packing machines, packages substantially in the form of a rectangular parallelepiped on are formed about the products, normally consisting of a group of twenty cigarettes arranged in three rows, or a group of ten packets of cigarettes arranged in two rows of five packets, from respective flat blanks, each having end lines defining an intermediate portion and two lateral portions on either side of the intermediate portion. Each lateral portion comprises a lateral panel connected to the intermediate portion along a respective bend line, hereinafter referred to as the "primary bend line"; and at least one outer portion extending outwards from a respective outer edge of the lateral panel and connected to it along a respective bend line hereinafter referred to as the "secondary bend line".
On known packing machines, each blank is folded about the product in a given number of successive stages, the first of which normally consists in positioning the blank with the intermediate portion facing a folding seat, and, by means of movable folding spindles with a bevel at the front, in folding the two lateral panels partially in a U about the respective primary bend lines and in contact with respective beveled input edges of the folding seat.
The above method involves several drawbacks, mainly due to the panels being substantially "jerked" about the respective primary bend lines, as consequence of the high output speed of modern packing machines, the extremely high operating speed of the folding spindles, and the fact that, despite the bend lines, the blanks, at least to begin with, remain extremely stiff.
A first consequence of the above drawback is that, instead of being folded, the two lateral panels may be pierced by the spindles, thus resulting in irreparable damage to the blank.
A further, and more frequent, consequence of the two panels being jerked about the bend lines is the "whiplash" effect this produces on the outer portions of each panel, and which, by virtue of at least part of the outer portions being inevitably results in fouling by drops of gum splashing off the outer portions.
Yet a further consequence of the above drawback is that, despite the spindles partially folding the lateral panels about the primary bend lines, the blank nevertheless remains stiff enough to hinder complete folding of the panels about the bend lines. As this is normally effected by inserting the product and the blank inside the folding seat, i.e. using the product itself as a reaction element, the residual rigidity of the blank may result in damage lo the product is it is inserted inside the folding seat.